Rubber product and method of making same



Patented Dec.- 8, 1931 UNITED STATES PATENT OFFlCE sums w. samba, or AKRON, AND

HABIAN L. TRUHBULL, OI HUDSON, OHIO, A8-

BIGNORS, BY mm: ASSIGNMENTS, '10 AMERICAN ODE INC 01 AKRON, OEIO, A

ooaroaarzon or nnnawm rubber industry at the present time because of the inability to utilize more fully the vast quantities of scrap rubber everywhere,

available at very low cost. Heretofore it has been a common practice to heat and at the same time to treat chemically scrap vulcanized rubber so as to remove any fabric therein and to devulcanize the rubber, then to wash, dry and refine by a grinding operation to produce a somewhat plastic mass. In this way, a reclaimed rubber so-called is produced which finds some limited uses in the em loyed commonly inthe manufacture of rub er goods, but an extended-use of. this product has not been found to be practical. The present invention provides a new way ofutilizing scrap vulcanized rubbers and one that is capable of producing rubber products of improved quality where the products are made entirely from vulcanized scrap, or, one which enables taining both new and scrap rubber,'while maintaining the quality of similar products made by prior processes.

In carrying out our invention, scrap vulcanized rubber, such as that from old tires, tubes, shoes, and the like, is softened or plasticized in any mannen adapted for the type of "scrap being employed, such as by digesting or masticating the scrap, either with or without heat and/or softening agents, or

by any of the so-called' reclaiming processes. When the rubber scrap contains fabric, it

is preferable before plastioizing the same to remove the fabric by grinding and mechanical picking of the fabric from.the rubber,

. V or the ground scrap may be subject to chemical'action to remove the fabric. Other im purities or foreign bodies may be removed in any suitable manner. The plasticized scrap prepared by whatever process is then er, such as defective, used and dismaking such prodthe use of larger propertions of vulcanized scrap in products con- "the plasticizing swam PRODUCT AND METHOD OF m6- SAIE Application filedAugust 24, 1928. Serial No. 801,848. a

dispersed in an aqueous medium to produce a dispersion of the scrap rubber, that is, the rubber in very fine particles is suspended on emulsified in a water phase containing emulsifying agents. f The plasticizing and emulsifying steps be coordinated by adding during the plasticizingstep ingredients which will serve as, or form with other ingredients, emulsifying agents for the scrap rubber dur- 00 ing the dispersion operation. Thus, a saponifiablc oil or resin, a fatty acid, or the like, may be used 0 effect, or assist in effecting, the plasticizing of the scrap, to which maybe added during plasticizing, or after- 06 ward, or during dispersion, an alkali which will form with the softener an emulsifying agent capable of accelerating and/or stabilizing the dispersion of scrap rubber particles in the liquid medium. 7 The vulcanized scrap now dispersed in liquid medium is in a condition to be made into useful products, which may be done by electrodepositing the rubber from the liquid dispersion upon .anodic molds, plates or screens, or the dispersed rubber particles may be deposited from the liquid medium by an other well-known means whether electricai: chemical or mechanical.

Where the rubber product to be made from the vulcanized scrap is not to be made from the scrap alone, other ingredients may be added at any stage of the process. Thus, in of the scrap such softening agents may be employed aswill impart beneficial properties to the final product. Other ingredients than softening agents may however be added during the plasticizing'operw tions, but we prefer to add the ingredients which it is desired to employ to modify the properties, of the end product to the emulsifiedvulcanized scrap rubber. Thus, the common compounding. ingredients, such as pigments, fillers, softeners, vulcanizing agents, accelerators and antioxidants, may be readily stirred into the emulsified scrap by first making a water paste or water dispersion thereof. Water dispersions of rubber, either natural or artificial; may also be added to the dispersed scrap,where desired.

, product is a viscous paste comprising rub-' I I three deposited In one embodiment of our process the following procedure is followed. Old inner tubesare ground and placed on a hotrubber-mill and masticated with the addition of a softener, such as aldol, alpha-naphthylamine, terpenes, mineral oils, vegetable oils, asphalts, kiln pine tar, pine tar oil, rosin oil' and similar substances until the mass assumes a smooth plastic condition, 5 per cent. by Weight of oleic acid may also be added to the mass during the plasticizin action.

This mass is then placed in a suita le masticator, such as of the internal mixer. type, and 100 parts of a 6% solution of ammonia gradually worked into the batch. This is followed by the slow addition of a 1% ammonia solution until an inversion of the rubber and water phases occurs. The resultant her in the disperse-phase and a water soap solution, with any other emulsifyin agents present, in the continuous phase, t e soap aving been formed by the action of ammonia on the oleic acid, the excess ammonia acting asa stabilizing agent of the dispersion.

Where a vulcanizable product is desired, an aqueous dispersion of sulfur and of other vulcanizing agent in suitable amounts may be mixed into this aqueous dis canized scrap rubber, suchor example as er cent. of sulfur, one-half per cent. organic accelerator, etc., on the dry weight of the scrap rubber, and treated scrap rubber dispersion then placed in an electrophoretic apparatusandthe dispersed particles electroat the anode of the apparatus. When dried and cured, the resulting product possesses a smooth firm texture.

In another embodiment of our.invention, ground tire casings are placed in a digester and treated with steam and a chemical capable of destroying the fiber and, after washing and drying, the rubber crumb is plasticized with a suitable softener. This plasticized vulcanized rubber 'is then placed in a masticating machine and five er cent. or more of sodium stearate or so ium-oleate, or other emulsifying agent admixed therewith. Mastication is continued with the slow addition of water until the rubber becomes dispersed in fine particles in the external aqueous phase. Stabilizing agents may be a ded to this dispersion if desired, and it may be diluted with water to form an emulsion of any desired consistency. Superior products may be made from this emulsifiedlvulcanized rubber by adding thereto dispersions of crude rubber and of vulcanizin agents, of which products the following are i lustrative (1) An aqueous emulsionoomprising the above-mentioned vulcanized rubber emulsion containing .95 parts dry weight of vulcanized rubber, was mixed with an emulsion containing 3 parts by weight of sulfur and per cent. 0 organic accelerator,

ersion of vuling be necessitate one part b weight of an organic accelerator and place in an electrophoretic apparatus and an efi'ectively unidirectional electric current of suitable current density 0.5 to 1 ampere per sq. cm.) passed throug the emulsion forming a sheet of rubber at the anode which, when dried and vulcanized, possessed a tensile stren h of '700 pounds per sq. in. and an elongation of 460'per cent.

(2) An aqueous emulsion comprising equal parts by weight of the above described vulcanized rubber emulsion and a crude rubber emulsion, the weights being computed as the dry weight of the solid content of the emulsion, two er cent. of sulfur and one-half based on the rubber content of was placed the emulsion,

in an electrophoretic apparatus and a sheet of rubber formed at the anode, which was dried and vulcanized to produce a sheet of firm smooth texture having a tensile strength of 2,440 pounds per sq. in. and an elongation of 775 per cent.

It is to be understood that the specific examples hereinabove are given merely by way of illustration and are in no we restrictive of applicants process which roadly involves a method of utilizing vulcanized rubber scrap by first bringing it to a plastic condition, dispersing the plasticized scrag in an aqueous medium, associating where esired modifying substances with the vulcanized scrap either before, during or after plasticizing or with the aqueous dispersion, and makfrom such dispersions of vulcanized scrap rubber useful products by precipitating therefrom the suspended particles thereof on a suitable deposit-receiving member by any suitable means, such as dipping, spreading, splgaying, extruding, electrophoresis and the The term rubber is used herein to include caoutchouc, balata, guttmpereha and other rubber-like gums from laticiferous plants. The term plasticized vulcanized scrap rubber indicates any form of waste or used vulcanized rubber which has been treated to convert it into a smooth plastic state whether or not other" materials have been added to or subtracted from the scrap before, during or after the treatment.

Numerous modifications and variations of the process herein described may be made without departing from the principles of this invention and we conse uently do not desire to limit the appended c aims except as may y the prior art.

We claim:

1. A process for making rubber products from vulcanized scrap rubber which comprises plasticizing the vulcanized rubber scrap, dispersing the plasticized scrap in fine particles in a liquid containing an emulsifying agent, coagulating the dispersed particles from the liquid emulsion by the migration of i'i i coagulating ions from a depositing base, and

the product.

process for makin rubber products from vulcanized scrap ru ber wh1ch comprises plasticizingl the vulcanized rubber scrap, dispersing t e plasticized scrap in fine particles in a liquid containing an. emulsifying agent, intimately mixing into said liquid dispersion other dispersions of ingredients capable of modifyingthe properties of the dispersed scrap rubber in the precipitated product, electrodepositin from the liquid emulsion dis ersed partic es, and drying the electrodeposlted product.

3. A process for makin rubber products from vulcanized scra ru her which comprises plasticizin t e vulcanized rubber scrap, dispersing t e plasticized scrap in fine particles in a liquid {containing an emulsif mg-agent, electrodepositing from the liquld emulsion dispersed-particles, and drying the electrodeposlted product.

4. A "process for makin rubber products from vulcanized scrap ru ber which comprises plasticizingl the vulcanized rubber scrap, dispersing t e plasticized scrap in.fine particles in a liquid containing an emulsifying agent, intimately mixing into said liquid dispersion other dispersions of ingredients capable of modifying the properties ofthe dispersed scra rubber in the precipitated product, inclu ing vulcanizing agents, thereafter coa ulating the dispersed particles of the liqui dispersion by the migration of coagulating ions from a depositing base, and drying and vulcanizing the precipitated composition to form a compact homogeneous product.

5. A process for making rubber products from vulcanized scrap rubber which comprises plasticizing the vulcanized rubber scrap, dlspersing the plasticized scrap in fine articles in a liquid containing an emulsifymg agent, intimately mixing/into said liquid dispersion other dispersions of ingredients capable of modifying the properties of the dispersed scra rubber in the precipitated product, inclu 'ng an aqueous dispersion of rubber, electrodepositing from the liquid emulsion the dispersed particles, and drying the electrodeposited product.

6. A process. for makin rubber products from vulcanized scrap rifiiber which comprises c'oagulatin the dispersed particles from an aqueous dispersion comprising scrap rubber, by the migration of coagulating zone from a depositing base.

7. A process for makin rubber products from vulcanized-scrap ru ber WhlCh comprises coagulating the dispersed particles from an aqueous dispersion comprising scrap rubber and natural rubber latex, by the mi-' gration of coagulating ions from a depositing base.

8. A process for making rubber products from vulcanized scrap rubber which comprises electrodepositin the dispersed particles from an aqueous ispersion comprising scrap rubber and natural rubber latex, on a de ition base. 7c 11 witness whereof we have hereunto set our hands this 24th day of July, 1928.

.JAMES W. SOHADE.

HARLAN L. TRUMBULL. 

